Multiproduct Firms and Market Structure
提出一种基于可观测市场特征的简单参数化方法，将水平产品差异化模型转化为可检验的预测，说明市场规模如何影响市场集中度，帮助判断模型是否具有实证内容。
Models of (horizontal) product differentiation generally admit many equilibria. These include concentrated equilibria, in which few firms each offer many products, andfragmented equilibria, in which many firms each offer one product. Since these outcomes depend in a delicate way on features of the models that are hard to identify or proxy empirically, these models may seem empirically empty in regard to predictions about industrial structure. This article proposes a simple and natural reparameterization of such models in terms of empirically observable market characteristics, thereby generating testable predictions about the relationship between market size and market structure (concentration).